Johns Hopkins researchers report that an analysis of
survey responses and health records of more than
10,000 American adults for nearly 20 years suggests
a “synergistic” link between exercise and good
vitamin D levels in reducing the risk of heart
attacks and strokes.

Both exercise and adequate vitamin D have long been
implicated in reducing heart disease risks, but in a
new study — one not designed to show cause and
effect — the researchers investigated the
relationship between these two health factors and
their joint role in heart health.

Their findings, which were published in the April 1
issue of The Journal of Clinical Endocrinology &
Metabolism, identified a positive and direct
relationship between exercise and vitamin D levels
in the blood, which may provide evidence that
exercise may boost vitamin D stores.

They also found that the two factors working
together seemed to somehow do more than either
factor alone to protect the cardiovascular system.

The researchers caution that their study is an
observational one and that long-term, carefully
controlled clinical trials would be needed to
establish evidence for cause and effect.

Nevertheless, the study does support the notion that
exposure to the “sunshine” vitamin D and exercise
are indicators of good health.

“In our study, both failure to meet the recommended
physical activity levels and having vitamin D
deficiency were very common” says Erin Michos, M.D.,
M.H.S., associate director of preventive cardiology
and associate professor of medicine at the Ciccarone
Center for the Prevention of Heart Disease at the
Johns Hopkins University School of Medicine.

“The bottom line is we need to encourage people to
move more in the name of heart health.”
Michos adds that exposure to a few minutes a day of
sunlight in non-winter seasons, eating a
well-balanced meal that includes oily fish, along
with fortified foods like cereal and milk, may be
enough to provide adequate levels of vitamin D for
most adults.

For their data analysis, the Johns Hopkins
researchers used previously gathered information
from the federally funded Atherosclerosis Risk in
Communities study beginning in 1987 and collected
from 10,342 participants initially free of heart or
vascular disease.

Information about participants was updated and
followed until 2013.
The participants were an average age of 54 at the
start of the study and 57 percent were women.
Twenty-one percent were African-American, with the
remaining participants identifying as white.

In the first visit between 1987 and 1989,
participants self-reported their exercise levels,
which were compared to the American Heart
Association recommendations of more than 150 minutes
per week of moderate intensity exercise or 75
minutes per week or more of vigorous intensity.

The researchers used the information to classify
each participant’s exercise level as adequate,
intermediate or poor.

Reviewing data from the second study visit by each
participant between 1990 and 1992, the researchers
measured vitamin D levels in the blood by detecting
the amount of 25-hydroxyvitamin D. Anyone with less
than 20 nanograms per milliliter of
25-hydroxyvitamin D was considered deficient for
vitamin D, and levels above 20 nanograms per
milliliter were considered adequate.
Thirty percent of participants had inadequate
vitamin D levels.

In the first part of their study, the Johns Hopkins
team showed that exercise levels positively
corresponded to vitamin D levels in a direct
relationship, meaning that the more one exercised,
the higher their vitamin D levels seemed.

For example, people with adequate exercise had an
average 25-hydroxyvitamin D level of 26.6 nanograms
per milliliter, those with intermediate exercise had
24.4 nanograms per milliliter, and those with poor
exercise had 22.7 nanograms per milliliter.

Those meeting recommended levels of exercise at
visit 1 had a 31 percent lower risk of being vitamin
D deficient at visit 2.

Yet, the researchers only saw such a positive
relationship between exercise and vitamin D in
whites and not African-Americans.

In the next part of the study, they found that the
most active participants with the highest vitamin D
levels had the lowest risk for future cardiovascular
disease.

Over the 19 years of the study, 1800 adverse cardiac
events occurred, including heart attack, stroke or
death due to heart disease or stroke.

After adjusting the data for age, sex, race,
education, smoking, alcohol use, blood pressure,
diabetes, high blood pressure medication,
cholesterol levels, statin use and body mass index,
the researchers found that those people who met both
the recommended activity levels and had vitamin D
levels above 20 nanograms per milliliter experienced
about a 23 percent less chance of having an adverse
cardiovascular event than those people with poor
physical activity who were deficient for vitamin D.

On the other hand, people who had adequate exercise
but were vitamin D deficient didn’t have a reduced
risk of an adverse event. In other words, the
combined benefit of having adequate vitamin D and
exercise levels was better than either health factor
alone.

But Michos says that sun exposure may not be the
whole story of the direct relationship found between
exercise and vitamin D levels, since vitamin D
produced by the skin after exposure to sunlight
tends to level off when the body makes enough, and
the levels in these participants didn’t show signs
of doing so.

She says this points to evidence that there may be
something else going on in the body that causes
vitamin D and exercise to positively influence
levels of each other.

For example, people who exercise may also have other
healthy habits that influence vitamin D levels such
as lower body fat and a healthier diet.
Alternatively, people who exercise may take more
vitamin supplements.

As for the racial disparity they saw, this could
mean promoting physical activity may not be as
effective for raising vitamin D levels in
African-Americans as in whites.

Michos notes that people with darker skin produce
vitamin D less efficiently after sun exposure,
possibly due to the greater amount of melanin
pigment, which acts as a natural sunscreen.

African-Americans also tend to have lower levels of
25-hydroxyvitamin D overall but they don’t seem to
experience the same consequences, such as bone
fractures, that whites have with similarly low
levels.

Michos cautions that people who meet the recommended
daily amount of 600 to 800 International Units a day
and who have adequate levels of vitamin D don’t need
to take additional vitamin supplements.

Michos notes that a recent randomized clinical trial
published in JAMA Cardiology failed to show any
cardiovascular benefit with high-doses of monthly
vitamin D supplements among participants living in
New Zealand.

“People at risk of bone diseases, have seasonal
depression, or are obese should have their
physicians measure vitamin D levels to ensure
they’re adequate, but for many, the best way to
ensure adequate blood levels of the vitamin is from
sun exposure, healthy diet, being active and
maintaining a normal body weight.”

She adds, “Just 15 minutes of sunlight in the summer
produces about 3000 international units of vitamin D
depending on latitude and skin pigmentation, which
is equivalent to 30 glasses of milk. Just be sure to
use sunscreen if you plan to be outside longer than
15 minutes.”

While the health boost from regular physical
activity is undisputed, the benefits of vitamin D
supplements haven’t yet been proven for heart
health.

She says that larger studies including more diverse
populations of patients and different dosing
regimens are currently on-going and, when published,
will provide further insight and guide
recommendations for patients.

Additional authors of the study included Kathleen
Chin, Di Zhao, Martin Tibuakuu, Seth Martin, Chiadi
Ndumele, Roberta Florido and Eliseo Guallar of The
Johns Hopkins University; Gwen Windham of the
University of Mississippi Medical Center and Pamela
Lutsey of the University of Minnesota.